The AGPL requires you to make the source code of your (web) application available under the same terms (AGPL). It is more strict about that than the regular GPL. For people that don't want to be bound by the terms of the AGPL, there is an alternative commercial license that can be purchased from Object Refinery Limited (it's not super-expensive, US$99.00 only). Since you are a non-profit, please send me some details offline and I may be able to give you a license for no cost.

I should add, for those reading along, that we're licensing JFreeSVG in this way as a means to fund our activities. JFreeChart has always been free, and a small percentage of people have supported that financially by purchasing the JFreeChart Developer Guide and Demo Source code. That has helped, but it has never been enough to fund JFreeChart development properly. That's why, now, we are putting other products (JFreeSVG, OrsonPDF, Orson Charts for Swing/JavaFX, Orson Charts for Android and Orson Charts for HTML5) in front of people and charging license fees for them. JFreeChart will remain free, but we want to grow our activities and we can't do that without making money, so that's what we are focusing on (as much as necessary anyway).